its elliptical
The Liver Bird, the emblem of Liverpool city in England, was probably originally an Eagle but it is now a Cormorant. See the Related Link.
Well, perching birds such as the songbird can be one. There are however more than 5000 types of species so predicting which type of birds are wheter if you studied ornithology.
ducks and others
Hummingbirds have nests that are the size of a quarter